Autoantibodies and other tests in rheum

Question 1

Scl-70 (anti-topoisomerase)

Answer 1

40% of diffuse scleroderma
15% limited
- higher risk of ILD

Question 2

RNA polymerase III

Answer 2

17% in scleroderma

• increased risk of renal crisis
• increased risk of malignancy

Question 3

anti-centromere antibodies

Answer 3

80% of limited scleroderma (CREST)

Question 4

Anti-Jo-1

Answer 4

Polymyositis

Anti-Synthetase syndrome

Question 5

Anti-Mi2

Answer 5

Dermatomyositis

Question 6

Pattern of ANA seen in limited systemic sclerosis?

Answer 6

Centromere

Question 7

Pattern of ANA seen in diffuse systemic sclerosis?

Answer 7

Speckled

Question 8

Pattern of ANA seen in poly/dermatomyositis?

Answer 8

Speckled

Question 9

Pattern of ANA seen in sjogrens?

Answer 9

Speckled

Question 10

Pattern of ANA seen in lupus?

Answer 10

Homogeneous and rim pattern most specific

Question 11

Anti-ds DNA

Answer 11

SLE

• highly specific but only 70% sensitive
• only 70% of patients with SLE have positive dsDNA

Question 12

Anti-histone antibodies

Answer 12

SLE

- often indicate drug induced lupus

Question 13

ANA pattern in RA

Answer 13

Homogeneous

Question 14

Most common and least specific ANA pattern

Answer 14

Speckled

Question 15

What tests are useful for monitoring SLE?

Answer 15

Anti dsDNA

Complement, ESR, renal function, urinalysis for protein

Question 16

What is considered a high titre ANA?

Answer 16

1:640

Question 17

Rheumatoid factor?

Answer 17

Rheumatoid arthritis
As sensitive as anti-CCP (around 70%) but less specific
Can be positive in:
Sjogrens
SLE
Hepatitis C, sarcoid, infective endocarditis, cryoglobulinemia

Question 18

Anti-CCP?

Answer 18

Specific for RA (more specific then RF but same sensitivity)

Predicts more erosive and more severe disease

Question 19

Anti-Ro/La

Answer 19

Sjogrens syndrome (70% sensitivity)
SLE (30% sensitivity)
- in SLE predicts higher rate of neonatal lupus (rash and complete heart block)
- women with anti-Ro antibody, carry a 3% chance of having a baby with neonatal lupus

Question 20

cANCA

Answer 20

anti-neutrophil antibody against proteinase-3

Granulomatosis with polyangiitis (90% sensitivity when disease is active, not used for monitoring)

Question 21

pANCA

Answer 21

anti-neutrophil antibody against myeloperoxidase
microscopic polyangiitis - 80% sensitivity
churg strauss - 60% sensitivity
* note atypical pANCA (not MPO) can be seen in inflammatory bowel disease

Question 22

Type 1 cryoglobulins

Answer 22

Monoclonal IgM or IgG

• caused by lymphoproliferative disorders Waldenstroms, MM, lymphoma
• not particulary good at activating complement so do not become clinically apparent until high enough to cause hyperviscosity

Question 23

Type 2 cryoglobulins

Answer 23

Monoclonal RF (usually IgM or IgA) against the Fc portion of IgG

• most associated with hep C and HIV
• most common type

Question 24

Type 3 cryoglobulins

Answer 24

Polyclonal RF against IgG

- most associated with underlying connective tissue disorders

Question 25

What is meant by mixed cryoglobulinemia?

Answer 25

Type 2 and 3

- types that involve RF

Question 26

What is a cryoglobulin?

Answer 26

Immunoglobulins that precipitate in the cold and dissolve on re-warming

Question 27

Complement levels in mixed cryoglobulinemia?

Answer 27

Low C4 and normal C3

Question 28

Complement levels in a lupus flare?

Answer 28

Low C3 and C4

• activation of classical pathway = both low
• activation of alternative pathway = low C3 and normal C4

Question 29

Complement findings in post strep GN?

Answer 29

Low C3 and normal C4